docs: def sparse(self, rows: np.ndarray = None, cols: np.ndarray = None, layer: str = None) -> scipy.sparse.coo_matrix:
  		"""
  		Return the main matrix or specified layer as a scipy.sparse.coo_matrix, without loading dense matrix in RAM
  
  		Args:
  			rows:		Rows to include, or None to include all
  			cols:		Columns to include, or None to include all
  			layer:		Layer to return, or None to return the default layer
  
  		Returns:
  			Sparse matrix (:class:`scipy.sparse.coo_matrix`)
  		"""
  		if layer is None:
  			return self.layers[""].sparse(rows=rows, cols=cols)
  		else:
  			return self.layers[layer].sparse(rows=rows, cols=cols)